Brett Morgan — whose HBO documentary on the Rolling Stones, “Crossfire Hurricane,” premieres tonight on the network — is already planning his next project: a doc on late Nirvana singer Kurt Cobain. Morgan tells us the film, expected to be out in 2014, is being shepherded by Cobain’s controversial widow Courtney Love. “Courtney is the one that brought me into this,” said Morgan at the Ziegfeld Theatre Tuesday night, adding he and Love started discussing the project in 2007. “We’ve been trying to find the right time to put this film together and the time is now . . . Kurt was not only an amazing songwriter and musician, he was an incredible artist and filmmaker. So we are going to do the movie sort of like a third-person autobiography — [as] if Kurt was around and making a film about his life.” Love recently shot down rumors of a Nirvana musical.